Compact conductor

ABSTRACT

Improved electrical conductor is formed by compacting concentric conductors which have outside wires with gages at least equal to the gages of the inside wires. Such a conductor with 37 or more wires may have the outer layer only, made up of square wires.

United States Patent [1 1 Pembcrton Sept. 18,1973

[ 1 COMPACT CONDUCTOR UNITED STATES PATENTS 587,764 8/1897 Short..174/129R v 1,943,087 1/1934 Potter 174/128 X 3,164,670 1/1965 Ege3,352,098 11/1967 Gilmore 174/130 X Primary Examiner-E. A. GoldbergAttorney-Victor F. Volk 57 ABSTRACT Improved electrical conductor isformed by compacting concentric conductors which have outside wires withgages at least equal to the gages of the inside wires. Such a conductorwith 37 or more wires may have the outer layer only, made up of squarewires.

5 Claims, 3 Drawing Figures cowrrxcr counucron BACKGROUND OF THEINVENTION The conductors of electric cables are customarily made bystranding together a plurality of wires in concentric layers. Thegeometry of the cable cross section is naturally such that six wireswill fit firmly around a single center wire, twelve wires will fitaround the six,

eighteen wires around the twelve, etc. each layer having six more wiresthan the underlying layer. Conductors made up in this manner are knownas concentric lay conductors and are described in a number of industrystandards, such as American Society for Testing Materials (ASTM) B 8-70.The number of wires in such a concentric lay conductor will equalexactly 3n 3n 1 where n represents the number of layers surrounding thecentral wire. Concentric lay conductors, however, have large overalldiameters for a given conductance, or cross section of metal, caused bythe many open spaces or interstices between the wires. To reduce theconductor diameter it has been known to crush or compact the wires afterthe layers have been applied, so as to force some of the metal into theinterstices. Conductors with wires so crushed are known as compact roundconductors. U.S. Pat. No. 1,943,087, which issued in 1934, is stillfairly representative of the state of the art of compact roundconductors and a number of industry standards, such as ASTM B 496-69describe them. Compacting of a standard conductor, however, changes thegeometrical dimensional relationships so that a layer with six morewires than the underlying layer no longer fits naturally onto theconductor. The aforementioned compact conductor patent teaches, and theteaching has been generally followed in commerce, that, to compensatefor the reduction in diameter of the conductor core by compacting, theindividual diameters of wires in succeeding layers should be reduced.This has had the significant manufacturing advantage that all the reelcarriers of the stranding machines are utilized, but it has also had theserious disadvantage that 'many' different wire sizes are required to bedrawn and stocked. Another disadvantageous practice of the known art ofmaking compact round conductors, as followed in commerce, and as taughtby the early patent, has been the necessity to reduce the length ofstranding lay substantially below the maximum allowed by ASTM and otherindustry standards. This is l 6 times the diameter for copper (see ASTMB 496-69) and for Class B strand aluminum (see ASTM B 400-70).Shortening 'of the lay adds significantly to the cost of manufacturingsince it reduces the hourly production of the stranding machines.

The aforementioned patent taught the art of compac'ting conductors bymeans of pressure rolls. More recently it has been known that it is alsofeasible to effect the compacting by pulling the conductor through awire drawingtype die after the application of each layer of wires, butconductors made by either method, using industry teachings for theselection of wire sizes and lay lengths, have been characterized by widevariations of temper, due to uneven work hardening, through theconductor section. Typically, the more central wires have beenexcessively hardened. When such conductors are flexed or tensioned theload is not evenly distributed and failure will occur earlier than itwould for a conductor of uniform hardness throughout its section.

SUMMARY I have invented a new compact electrical cable conductor andmethod that reduces the number of differ ent wire sizes to be drawn andpermits a maximum stranding lay for each layer. My conductor has areduced diameter for a given conductance and a relatively uniform degreeof work hardening in each layer. Copper conductor, compacted to myinvention, has retained an elongation averaging over 15 percent in eachlayer, although the diameter is reduced even below that of prior artconductors in which some wires retained elongations of less than 5percent. My present conductor comprises a central wire and a pluralityof layers of helically applied wires surrounding the central wire. Aninnermost of these layers consists of six wires and each additionallayer comprises a plurality of wires six in number greater than thenumber of wires in the directly underlying layer. The gage of theindividual wires in any layer of my conductor is not less than the gageof any underlying wire and the conductor is compacted to a diameter atleast 8 percent less than the diameter of a concentric lay conductor ofequal circular mil area. Embodiments of my conductor compriseconstructions wherein the central wire and all the wires in the layersare round and of the same gage before compacting, and constructions ofthree or more layers wherein the wires of the outermost layer, only, aresquare and of a larger gage. In preferred embodiments the wires in myconductor comprise copper and the layers alternate in direction of lay.

My method for making a compact conductor for an electric cableconsisting of 3n 3n 1 wires helically wound in n layers over a centralof said wires comprises steps of continuously pulling the central wirefrom a supply thereof through n fixed, linearly mounted, wire drawingtype dies, pulling six round wires, of a sectional area at least aslarge as the sectional area of the central wir'e'from supplies of thesame being driven in rotation around the central wire, througha'first ofthe dies, and therein forming a compacted core from the wires. Thisfirst die has a minimum aperture no greater than 92 percent of threetimes the diameter of the central wire. In my method I also pull twelveround wires each having a sectional area at least as large as thesectional area of one of the six wires, from supplies driven in rotationaround the core through a second of the dies therein compacting thewires and enlarging the core. This second die has a minimum aperture nogreater than 92 percent of five times the diameter of the central wire.For each of any additional layers I pull a plurality of wires six innumber greater than the number of wires in the next underlying layerthrough one of the plurality of dies having a minimum aperture no largerthan 92 percent of (2m l) times the diameter of the central wire where mrepresents the layer number. Each of these additional layer wires is atleast as large in sectional area as any of the underlying wires and ispulled from supplies being driven in rotation around the core.

BRIEF DESCRIPTION OF THE DRAWING:

FIG. ll shows a section of a conductor of my invention.

FIG. 2 shows a section of another embodiment of the conductor of myinvention.

FIG. 3 shows steps in the method of my invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS As seen in FIG. 1, acompact conductor of my invention indicated by the numeral has a centralwire 11 surrounded by three layers 12, 13, 14 or wire wrapped helicallyaround it. Prior to compacting, the wire 11 and all the wires of thelayers 12-14 are round. FIG. 2 shows another embodiment of my conductordiffering from that of FIG. 1 by having an outside layer 16 of squarewires. An essential feature wherein my conductors difier from priorcompact round conductors resides in the fact that the wires of the outerlayers 14, 16

are no smaller in cross-section or gage than the wire 1 1. Beneficially,all the round wires are the same gage. To form the conductor 10 thecentral wire 11, along with six identical wires of the layer 12, arepulled through a wire drawing type die 17 which compresses or compactsthe strand at least 8 percent, creating the sectional appearance ofFIGS. 1 and 2, wherein the interstices between the wires have beensubstantially filled with metal by deforming the initial circular shapeof both the wire 11 and the wire of the layer 12. The die 17 anddownstream dies 18, 19, 21 to be further described are mounted rigidlyin line and the wires are pulled through the dies at a predeterminedrate by capstan means, not shown, associated with a stranding machinesuch as a type of machine known as a rigid strander on which six reelsholding supplies of the wires of the layer 12 are rotated around theline of the central wire 11 as the wires are pulled off into the die 17.In a like manner, but in the opposite direction of rotation, 12 roundwires of the layer 13 are rotated around a compacted core 22 beingpulled into the die 18. Eighteen wires of the layer 14 are rotated toapply a left hand lay into the die 19 completing the conductor 10. Themethod of FIG. 3 can be applied to an indefinite number of layers asshall be further explained with examples hereinbelow. 1 have shown theapplication of an additional layer of 24 wires 23 of the same size asthe wire 11 through a wire drawing type die 21 with a right hand lay. Itis a feature of my invention that a superior compact conductor can beformed of copper wires with the direction of lay alternated to balancethe construction. ASTM B 496-69, the industry standard for compact roundcopper conductors has followed the teaching of the U.S. Pat. No.1,943,087 patent that the layers should all have the same direction oflay and my invention, involving the application of full size wires orlarger in the outer layers also has advantages for such a unildyconstruction. It should be noted that ASTM B 400-70, for aluminumcompact round conductors has permitted the alternation of layers,presumably because of the softer metal. Example 1, below, typifies acopper conductor made from round wires in accordance with my invention.

EXAMPLE 1 1 Conductor size, 500 MCM, 37 wires Diameter of each of theround wires, inch, 0.1247 Aperture of die 17 over six wires, inch, 0.316Length and direction of lay of six wires, 4.74 inches L.1-1. Aperture ofdie 18 over 12 wires, inch, 0.526 Length and direction of lay of '12wires, 7.89 inches, R11.

Aperture of die 19 over 18 wires inch, 0.736

have a perimeter of only 18 X 0.6113 X sin 10 Length and direction oflay of 18 wires, 1 1.04 inches,

A detailed consideration of EXAMPLE 1 will clarify some of the featuresof my invention. The total number of wires are thirty seven and thenumber of layers over the central wire are three. This corresponds tothe formula for a concentric strand, S 3n 3n 1, where n represents thenumber of layers and S the number of wires. The diameter over the secondlayer of an uncompacted strand would be (2m 1) times the wire diameterwith m equal to 2 or, 5 X 0.1247 0.6235 inch, the pitch diameter of thenext layer would equal 0.6235 0.1247 equals 0.7482 inch. An 18 sidedpolygon inscribed in a circle of this diameter would have a perimeter of18 X 0.7482 X sin 10 2.326 inches. The sum of the diameters of 18strands of 0.1247 inch wires equals 2.245 inches, allowing the 18strands to fit an uncompacted core with an allowance for the lay angle.In the compacted core of EXAMPLE 1 however, the die 19 has an apertureof only 0.736 inch, if we obtain the pitch diameter by subtracting onewire diameter (0.1247) from this aperture we obtain 0.61 13 inch. An 18sided polygon inscribed in a 0.61 13 inch circle will 1.9107 inches.Since, as has been stated, the 18 wires require a perimeter of 2.245inches, they must be crushed together even before entering the die 19. 1have found, surprisingly, that it is not only possible to introducewires of this large diameter, but that so doing produces a more compactconductor and one in which there is no excessive work hardening.

EXAMPLE 2 Conductor size, Awg No. 1/0, 19 wires Diameter of each roundwire, 0.0817 inch Aperture of die 17 over six wires, 0.204 inch Lay ofsix wires, 3.24 inches R.1-I.

Aperture of die 18 over 12 wires, 0.340 inch Lay of 12 wires, 5.31inches L.l-1.

EXAMPLE 3 Conductor size, Awg No. 2/0, 19 wires Diameter of each roundwire, 0.0915 inch Aperture of die over six wires, 0.229 inch Lay of sixwires, 3.47 inches RH. Aperture of die over 12 wires, 0.382 inch Lay oftwelve wires, 5.93 inches L.H.

EXAMPLE 4 Conductor size, Awg No. 4/0, 19 wires Diameter of each roundwire, 0.1 153 inch Aperture of die over six wires, 0.288 inch Lay of sixwires, 4.06 inches R.l-l. Aperture of die over 12 wires, 0.480 inch Layof 12 wires, 7.61 inches. L.1-1.

EXAMPLE 5 Conductor size, 750 MCM, 61 wires Diameter of each round roundwire, 0.1215 inch Aperture of die over six wires, 0.302 inch Lay of sixwires, 4.53 inches, RH.

Aperture of die over 12 wires, 0.503 inch Lay of twelve wires, 7.55inches L.H.

Aperture of die over 18 wires, 0.705 inch Lay of eighteen wires, 10.58inches R.l-1. Aperture of die over 24 wires, 0.906 inch Lay of 24 wires13.59 inches, L11.

l have found that where there are three or more layers over the centralwire an increased surface smoothness of the conductor and a lessening ofthe pulling load of the stranding machine can be achieved by drawing thewires in the outer layer square, instead of round. The same number ofwires are used in the layer as would be used for a conventionalconcentric strand i.e. 6m wires, where m represents the number oflayers, and the sectional area of the square wire is at least as greatas any of the other wires in the conductor, in fact, I prefer toincrease the area in the square wires as illustrated in EXAMPLES 6-10below.

EXAMPLE 6 Conductor size, 250 MCM 37 wires Diameter of each round wire0.0855 inch, area Aperture of die over six wires, 0.228 inch Aperture ofdie over 12 wires, 0.380 inch Lay of 12 wires, 5.89 inches, RH.

Side of square wires 0.0794 inch, area 0.005961 in Aperture of die over18 square wires, 0.522 inch Lay of 18 wires 8.04 inches, L.l-l.

deducted for rounded comers per ASTM B 4868 EXAMPLE 7 Conductor size,350 MCM, 37 wires Diameter of each round wire, 0.1010 inch Die apertureover six wires, 0.270 inch Die aperture over 12 wires, 0.450 inch Lay of12 wires, 6.90 inches, RH. Side of square wires 0.0940 inch Die apertureover 18 square wires 0.616 inch Lay of square wires, 9.57- inches, L.H.

EXAMPLE 8 Conductor size, 500 MCM, 37 wires Diameter of each round wire,0.1210 inch Die aperture over six wires, 0.325 inch Die aperture over 12wires 0.540 inch Lay of twelve wires, 8.06 inches R.l-l. Side of squarewires 0.1 120 inch Die aperture over 18 square wires 0.736 inch Lay ofsquare wires 11.02 inches, L.l-l.

' EXAMPLE 9 Conductor size, 750 MCM, 61 wires Diameter of each roundwire, 0.1153 inch Aperture of die over six wires, 0.307 inch Aperture ofdie over 12 wires, 0.512 inch Aperture of die over 18 wires, 0.717 inchLay of 18 wires 10.57 inches, R.H.

Side of square wires 0.1060 inch Lay of 24 square wires 14.16 inchesL.H. Die aperture over square wires, 0.906 inch EXAMPLE l0 Conductorsize 1000 MCM, 61 wires Diameter of each round wire, 0.1330 inchAperture of die over six wires, 0.358 inch Aperture of die over 12wires, 0.597 inch Aperture of die over 18 wires, 0.836 inch Lay of 18wires, 12.34 inches R.l-l.

Side of square wires, 0.1225 inch Die aperture over 24 wires, 10.56inches Lay of square wires 16.40 inches L.l-1.

In addition to the benefits of high production speeds and lowerdiameters already mentioned, I have found that running compact roundconductors with large outside wires has the unexpected result that thestrand remains tight on the strander capstan during reel changes, can bestranded without adding oil for lubricant, and gives excellent die wear.

The dies 17, 118, 19, 211 differ from commonly used wire drawing dies inhaving larger apertures but they are characterized with wire drawingdies in being formed of tungsten carbide or material of similarhardness, having highly polished smooth inner surfaces, widened entrancezones 101., cylindrical or substantially cylindrical lands 102, and,preferably, conical reliefs 103.

I have invented a new and useful compact round conductor for electriccables, and a new method of making such conductor of which the foregoingdescription has been exemplary rather than definitive and for which Idesire an award of Letters Patent as defined in the following claims.

I claim:

1. A conductor for an electric cable comprising:

A. a central wire and a plurality of layers of helically applied wiressurrounding said central wire, an innermost of said layers consisting ofsix wires and each additional layer consisting of a plurality of wiressix in number greater than the number of wires in the directlyunderlying layer,

B. the gage of individual wires in any layer being not less than thegage of any underlying wire, and

C. said conductor being compacted to a diameter at least 8 percent lessthan the diameter of a concentric lay conductor of equal circular milarea.

2. The cable of claim 1 wherein said central wire and all of said wiresin said layers are round and of the same gage before compacting.

3. The cable of claim 1 comprising at least two of said layers of roundwires of the same gage as said central wire and an outer of said layersof square wires of a larger gage, before compacting.

4. The cable of claim 1 wherein all of said wires comprise copper.

5. The cable of claim 4 wherein said layers alternate in direction oflay.

i '8 i l l 1 L1 1.), E',/\'"- n 0 i arr" ""r ("1 1.12.3021; f 1!.. a.fix. i1; .5; 'rz:=.'.:.r=:niz No. 3 r I 093 Ejmxxl September 18 1973 i lI Denver L. Pemberton Inventofla) It is certified that error appears inthe above identified patent and that. said Letters Patent nre herebycorrected as shown below:

Column 3, line 6: cancel "or" and insert -of-.

line 23; cancel "wire", second occurrence, and

insert -wires--,

line 51: cancel "unildy" and insert unilay.

Column 4,1ine 60; cancel "round" second occurrence.

Column 6, line 14: cancel/"10.56" andinsert -l.056-- y Claims 2,3,4, and5; line 1, cancel "cable" and insert -conductor-.

*-- Signed and sealed this 12th day of February 1974.

l (SEAL) Attest:

EDWARD M. FLE TCHERJRn Attesting Officer 0 MARSHALL DANN Commissioner ofPatents Fiiilftlil'. I-Eo. 1211191 September 18 1973 l lnventofls.)Denver L. Pembierton It is certified that error appears in the 'aboveidentifiecl patent o i and that said nczucrs PltQllE ore nercbycorrected as shown below:

Column 3, line 6: cancel "or" and insert -of.

line 23; cancel "wire", second occurrence, and

insert wires-.

line 51: cancel "unildy" and insert --unilay-.

Column 4,1ine 60; cancel "round" second occurrence.

Column 6, line 14: cancel "lO.56" andinsert --l.056.

Claims 2,3,4, and 5; line 1, cancel "cable" and insert conductor.

* Signed and sealed this 12th day of February 1974.

(SEAL) Attest:

EDWARD M. FLEITCHER RO Attesting Officer C MARSHALL DANN Commissioner ofPatents

1. A conductor for an electric cable comprising: A. a central wire and aplurality of layers of helically applied wires surrounding said centralwire, an innermost of said layers consisting of six wires and eachadditional layer consisting of a plurality of wires six in numbergreater than the number of wires in the directly underlying layer, B.the gage of individual wires in any layer being not less than the gageof any underlying wire, and C. said conductor being compacted to adiameter at least 8 percent less than the diameter of a concentric layconductor of equal circular mil area.
 2. The cable of claim 1 whereinsaid central wire and all of said wires in said layers are round and ofthe same gage before compacting.
 3. The cable of claim 1 comprising atleast two of said layers of round wires of the same gage as said centralwire and an outer of said layers of square wires of a larger gage,before compacting.
 4. The cable of claim 1 wherein all of said wirescomprise copper.
 5. The cable of claim 4 wherein said layers alternatein direction of lay.